Speaker 1: Welcome to tech Stuff, a production from iHeartRadio. Hey there,
Speaker 1: and welcome to tech Stuff. I'm your host, John Vin Strickland.
Speaker 1: I'm an executive producer with iHeartRadio and how the tech
Speaker 1: are you. It is time for a classic episode of
Speaker 1: tech stuff, and that means we're gonna be taking a
Speaker 1: look at how solar towers work. This episode originally published
Speaker 1: on March ninth, twenty sixteen. It's an interesting way of
Speaker 1: harnessing energy from the Sun that does not involve directly
Speaker 1: transmitting or translating photons to electricity the way a solar
Speaker 1: panel would. So sit back and enjoy this classic episode
Speaker 1: of tech stuff. Today, I want to talk a little
Speaker 1: bit about solar towers, which is a different way of
Speaker 1: harnessing the Sun's energy, and I think it's a really
Speaker 1: clever way as well, because it doesn't rely on sunlight
Speaker 1: hitting a panel. Obviously, the big big drawback to that
Speaker 1: approach is when the sun isn't hitting a panel, you're
Speaker 1: not generating any electricity. Right, So if it's super cloudy
Speaker 1: or if it's nighttime, if the sun is not able
Speaker 1: to hit the panel, the sunlight's not getting there, you
Speaker 1: have nothing to convert into electricity and your solar panels
Speaker 1: go on to be unused for that duration. So that
Speaker 1: can be really rough if you have a long stretch
Speaker 1: of overcast days, or you live in a place where
Speaker 1: you don't get solar exposure at your house because of
Speaker 1: maybe they're taller buildings around you, or trees or whatever
Speaker 1: it may be. Maybe you have a north facing house
Speaker 1: rather than a south facing house here in the Northern Hemisphere.
Speaker 1: If you have a south facing house in the Northern Hemisphere,
Speaker 1: you're going to get more solar exposure than a north
Speaker 1: facing house, So solar panels have that drawback. They're also
Speaker 1: there's efficiency issues with solar panels. When we talk about efficiency,
Speaker 1: what we mean is how much of the sun's energy
Speaker 1: can we actually convert into electricity and how much of
Speaker 1: it do we lose? How much of that energy bounces
Speaker 1: off the panel and we do not capture it. Most
Speaker 1: commercial solar panels, the kind that you would put on
Speaker 1: your house, the efficiency is around eleven to fifteen percent,
Speaker 1: meaning that you're losing a lot, like eighty five percent
Speaker 1: of that energy is not converting into electricity. What that
Speaker 1: means is that you have to buy more solar panels
Speaker 1: to cover more space to collect more solar energy to
Speaker 1: generate enough electricity to meet your needs. Obviously, if solar
Speaker 1: panels were one hundred percent efficient, which is impossible by
Speaker 1: the way, physically impossible. People have proved it with masth,
Speaker 1: then if it were one hundred percent efficient, you wouldn't
Speaker 1: need as many solar panels in order to do what
Speaker 1: you need to do. That's just not the case in reality. Instead,
Speaker 1: we often have to buy more than what we would
Speaker 1: like cover a larger area. And even then again you're
Speaker 1: limited to collecting electricity or generating electricity i should say,
Speaker 1: during the daylight hours. An electricity also is a use
Speaker 1: it or lose it kind of thing, meaning that if
Speaker 1: you don't have an immediate use for that electricity and
Speaker 1: you don't have a way to store it, you lose
Speaker 1: that electricity. You have to use it when it's generated,
Speaker 1: so you need to have some sort of battery system
Speaker 1: as well, so that in the times when you're not
Speaker 1: using the electricity you're generating, you can still save it
Speaker 1: for later use. And until recently, batteries have been really
Speaker 1: expensive for the home, but Tesla's powerwall has kind of
Speaker 1: led a revolution in that space and we're starting to
Speaker 1: see more affordable versions of batteries hit the home market. Okay,
Speaker 1: all that's out of the way to just say that
Speaker 1: the traditional solar panel approach has its drawbacks. Now, let's
Speaker 1: talk about solar towers, because they take a totally different
Speaker 1: approach to harnessing electricity from the sun, and it's really
Speaker 1: pretty clever. And they can harness electricity or they can
Speaker 1: generate electricity day or night. So you might wonder, well,
Speaker 1: how is that possible? And when the Earth rotates so
Speaker 1: that the sun is no longer shining on a solar tower,
Speaker 1: where's that electricity coming from. So here's the way it works. Now,
Speaker 1: I'm largely going to refer to a company called Solar Reserve,
Speaker 1: which is here in the United States. Solar Reserve is
Speaker 1: just one company that is building structures like these around
Speaker 1: the world, So I don't mean to suggest they're the
Speaker 1: only one. I'm using them as the example because that
Speaker 1: so much of their information is available to actually read
Speaker 1: about and understand. So it's a really helpful approach. Solar towers. Well,
Speaker 1: first of all, the name kind of gives away the
Speaker 1: main feature. There's a tower at the center of this
Speaker 1: structure or really multiple structures. So how tall are these
Speaker 1: hours Well, according to Solar Reserve, the height of the
Speaker 1: tower and its thermal receiver. More on that in just
Speaker 1: a second tends to be six hundred forty feet combined,
Speaker 1: or about one hundred and ninety five meters. So you've
Speaker 1: got this tower in a large area. You want to
Speaker 1: have an area that gets a lot of solar exposure,
Speaker 1: otherwise this is not a practical way of generating electricity.
Speaker 1: So imagine like a desert, nice flat desert, lots of
Speaker 1: sunlight hitting that dessert every typical day, and you have
Speaker 1: a tall tower with a receiver on the top of it.
Speaker 1: Now that receiver is actually a series of dark panels.
Speaker 1: And these aren't solar panels, not in the way that
Speaker 1: you would put on top of your house. They are
Speaker 1: not converting sunlight into electricity directly. Rather, they are panels
Speaker 1: that transfer thermal energy. In other words, they're all about
Speaker 1: transmitting heat. So these panels have sixty six thin wall
Speaker 1: straight tubes in them. Those tubes are designed to conduct
Speaker 1: heat from the outside to the inside of that tower,
Speaker 1: and the tubes are made out of a steel alloy
Speaker 1: that's covered in a high absorptivity black coating to maximize
Speaker 1: the amount of energy the panel can absorb. So you've
Speaker 1: got sunlight shining on this tower, Well, how is that
Speaker 1: enough to generate electricity on its own. It's not. In fact,
Speaker 1: what you end up doing is surrounding the tower with mirrors. Now,
Speaker 1: Solar Reserve uses mirrors that they call heliostats. These heliostats
Speaker 1: are mounted on arms essentially that allow them to track
Speaker 1: the motion of the sun. That way, the mirrors maintain
Speaker 1: the ideal angle to reflect the sun's light directly toward
Speaker 1: the top of that tower at that receiving point of
Speaker 1: the tower on those panels. And we're talking about a
Speaker 1: lot of mirrors. Solar Reserve has one area called the
Speaker 1: Crescent Dunes. That's their tower that they have in the US,
Speaker 1: and the Crescent Dunes towers surrounded by more than ten
Speaker 1: thousand mirrors, covering a fifteen hundred acre field. So this
Speaker 1: is a big operation. You've got to have a lot
Speaker 1: of open land for this to work. That's obviously one
Speaker 1: of the potential drawbacks, right that you need a place
Speaker 1: that's going to have a lot of solar exposure, and
Speaker 1: you need to have enough space to make it make sense.
Speaker 1: But assuming you have both of those things, you can
Speaker 1: do something pretty incredible. We'll be back with more about
Speaker 1: how solar towers work after these messages. So what these
Speaker 1: mirrors do is direct that sunlight up at those dark
Speaker 1: panels I was talking about. Remember I mentioned there were fourteen.
Speaker 1: These fourteen panels are divided up into two groups of seven.
Speaker 1: Each group of seven represent kind of a circuit, and
Speaker 1: that circuit is not for electricity. It's rather for a
Speaker 1: circuit of pipes that are circulating liquid salts. So liquid
Speaker 1: salts are pretty cool, which is a weird way of
Speaker 1: putting it when you're talking about thermal energy, But liquid
Speaker 1: salts can hold on to more heat than water can
Speaker 1: and can remain in liquid form, so in other words,
Speaker 1: they don't vaporize into steam. And what solar reserve does
Speaker 1: is it pumps around five eight hundred gallons of liquid
Speaker 1: salts per minute through the receiver circuits that run back
Speaker 1: and forth across the inside of these black panels. So
Speaker 1: imagine you've got this really tall tower. At the top
Speaker 1: of the tower, you have these fourteen dark panels, and
Speaker 1: then let's just take seven on one side. You've got
Speaker 1: seven of those dark pounds on one side. On the
Speaker 1: inside of those panels, you would see this criss crossing
Speaker 1: of a pipe that is circulating liquid salts through the pipe.
Speaker 1: Heat from the outside comes into the tower and it
Speaker 1: begins to heat those liquid salts running through that circuit.
Speaker 1: It's a simple heat transfer. And if you've listened to
Speaker 1: our podcasts about things like refrigerators and air conditioners, you
Speaker 1: know about you know how this, what the principles are,
Speaker 1: how how this is based same basic thing. You want
Speaker 1: to give as much surface area you know you want
Speaker 1: to you want to dedicate as much surface area as
Speaker 1: you can to heat and have the liquid salts cross
Speaker 1: over as much of that surface area as as possible
Speaker 1: to heat up the liquid salts. As the liquid salts
Speaker 1: move through the circuit, they become molten, so incredibly high temperatures.
Speaker 1: So the low side of the temperatures for these liquid
Speaker 1: salts is five hundred and fifty degrees fahrenheit or two
Speaker 1: hundred eighty eight degrees celsius. That's the low end. That's
Speaker 1: that's the chili side. If you want to talk about
Speaker 1: how hot they get, they can get up to a
Speaker 1: thousand ifty degrees fahrenheit or five hundred and sixty six
Speaker 1: degrees celsius. That's really impressive. And so you've got this
Speaker 1: massive amount of stored thermal energy. It's all inside the
Speaker 1: molten salts. So you've got a lot of heat stored up.
Speaker 1: What good is heat, Well, you can use heat to
Speaker 1: do the same thing that is done in power plants
Speaker 1: all over the world. You use heat to turn water
Speaker 1: into steam and use the steam to turn a turbine,
Speaker 1: which generates electricity. It's an incredibly simple idea. It's the
Speaker 1: basis of almost every other type of power plant, with
Speaker 1: the exception of things like solar panels that are used
Speaker 1: in solar farms. Like that's generating electricity straight from sunlight,
Speaker 1: as opposed to using that electricity to somehow turn water
Speaker 1: into steam. That would be ridiculous. You would lose way
Speaker 1: too much energy in that approach. But things like coal
Speaker 1: fired plants, even nuclear power plants, you're talking about generating
Speaker 1: electricity by heating up water into steam and using that
Speaker 1: steam to turn a turbine to do work, and that
Speaker 1: turbine ends up being an electric generator and you get
Speaker 1: electricity from that. So the purpose of the solar tower
Speaker 1: is really just to collect heat that's it. It's not
Speaker 1: doing anything magical. It's just generating tons and tons of heat.
Speaker 1: I know that tons is not really a unit when
Speaker 1: it comes to heat or temperature, but you understand what
Speaker 1: I mean. It creates an enormous amount of heat, and
Speaker 1: the molten salts then go into a big storage tank.
Speaker 1: And it's pretty cool because that storage tank ends up
Speaker 1: being a way of holding onto the heat for a
Speaker 1: long time. According to Solar Reserve, the company says that
Speaker 1: the molten salt only loses one degree of fahrenheit or
Speaker 1: about point five, five, five, etc. Etc. Degrees celsius in
Speaker 1: heat per day. So, in other words, if you have
Speaker 1: a long stretch of over days, you still have this
Speaker 1: massive vat. Really tank, it's not a vat, it's a
Speaker 1: tank because it's completely enclosed of molten salts and they
Speaker 1: hold onto that heat, which means you can continuously pump
Speaker 1: that through your water tank in order to heat water
Speaker 1: up to steam. And when I say pump it through,
Speaker 1: it's a very similar circuit that you would find at
Speaker 1: the top of the receiver. The molten salts don't mix
Speaker 1: with the water. Instead, you have a pipe that runs
Speaker 1: through the water tank. The molten salts run through the
Speaker 1: pipe and transfer some of their heat to the water
Speaker 1: through the material of the pipe itself. So you're not
Speaker 1: laying the molten salts in the water mixed together. That
Speaker 1: would be ridiculous. Instead, you're having the molten salts move
Speaker 1: through a pathway, and as they move through that pathway,
Speaker 1: they heat up the water. The water turns, the steam
Speaker 1: turns the turbine. Then the steam goes through a condenser
Speaker 1: to condense the steam back into water and goes back
Speaker 1: into the water tank. So once you use the molten
Speaker 1: salts to transfer some of this heat, they've lost that
Speaker 1: thermal energy. They're now moving into a different tank. It's
Speaker 1: a tank to pump the liquid salts back up into
Speaker 1: the top of the tower. So the neat thing with
Speaker 1: this system is that you can use it to deliver
Speaker 1: electricity day or night. You've got so much stored heat.
Speaker 1: After you get the system up and running and it's
Speaker 1: generated enough molten salt, like it's created enough molten salt
Speaker 1: through this process to allow this to happen, you can
Speaker 1: deliver electricity on demand twenty four hours a day, and
Speaker 1: that's how all power plants work. They deliver electricity on demand.
Speaker 1: They're not set to a certain level, and then if
Speaker 1: you don't meet that level, they you know, just that
Speaker 1: electricity goes to waste. They base it upon what the
Speaker 1: current demand. And I don't mean that as a pun,
Speaker 1: but it came out of that way. Chris would be
Speaker 1: so proud. They don't. They respond to whatever the demand
Speaker 1: and is at that time to produce the amount of
Speaker 1: electricity needed. So super interesting way of doing this by
Speaker 1: using the sun as an energy source to create the
Speaker 1: heat needed to turn water into steam and turn a turbine,
Speaker 1: as opposed to a fossil fuel like coal or oil,
Speaker 1: or a nuclear fuel in the case of nuclear fusion. Now,
Speaker 1: if we ever are a fission, I should say nuclear fission.
Speaker 1: I know all of you were ready to write in,
Speaker 1: and you should be because that was a silly mistake
Speaker 1: I made nuclear fusion. If we ever crack that nut,
Speaker 1: solar towers may seem quaint in comparison, but that's a
Speaker 1: very difficult problem in physics to solve. So we're still
Speaker 1: waiting on that. We'll conclude our episode on how solar
Speaker 1: towers work after these brief messages. So the neat thing
Speaker 1: about this obviously is that if you do have that
Speaker 1: amount of space, you can really offset a lot of
Speaker 1: a community's electricity needs with a solar tower. And the
Speaker 1: company thinks that the lifespan of these solar towers is
Speaker 1: somewhere in the area of about thirty years, meaning that
Speaker 1: after thirty years you would have to start to replace
Speaker 1: parts because just of wear and tear, or they would
Speaker 1: not be as efficient as they had previously been. So,
Speaker 1: for example, those panels, if the panels become less efficient
Speaker 1: at transferring heat over time, you would definitely want to
Speaker 1: replace them because you would be transferring less heat to
Speaker 1: generate your molten salts will be at a lower temperature.
Speaker 1: It would require more of them to turn water into steam,
Speaker 1: who become less efficient overall. So you have to make
Speaker 1: sure that all the parts are working. They're very few
Speaker 1: moving parts, which is awesome, but you have to make
Speaker 1: sure they're working throughout the lifetime of the facility and
Speaker 1: then obviously replace parts as needed. So the question then
Speaker 1: becomes doesn't make financial sense to switch over to using
Speaker 1: solar towers at least to offset electricity generation in a
Speaker 1: particular area. To answer that question, you have to look
Speaker 1: at a lot of different factors, and it is way
Speaker 1: more complicated than just a simple yes or no. For
Speaker 1: one thing, how much solar exposure is the area getting. Obviously,
Speaker 1: if you're not getting a lot, then that's not going
Speaker 1: to be a good choice for solar towers or a
Speaker 1: good place to put a solar tower. I should say
Speaker 1: also not just where, and you know what time of
Speaker 1: year do you get solar exposure? Those would be two
Speaker 1: big things. But how much does electricity cost in that
Speaker 1: region already? And the reason why you have to ask
Speaker 1: that question is if you were to provide electricity through
Speaker 1: the solar reserve system, would it make financial sense to
Speaker 1: make that switch? If coal is incredibly cheap in the area,
Speaker 1: and financially it might make more sense to stick with coal,
Speaker 1: even though we all know there are big environmental drawbacks
Speaker 1: to using coal. You create a lot of fossil fuels,
Speaker 1: you have a big carbon footprint that way, But it's
Speaker 1: hard to argue with the dollar cost of energy. If
Speaker 1: that dollar cost is higher with solar reserve, that's a
Speaker 1: tough sell because not everyone's willing to spend more money
Speaker 1: to keep their homes supplied with electricity just so that
Speaker 1: they have a lower carbon footprint with the electricity generation.
Speaker 1: It's just the truth of the matter, and some people
Speaker 1: don't have the money to afford the luxury. Obviously, now,
Speaker 1: if solar reserve is able to be significantly less expensive
Speaker 1: than whatever the alternatives are, that's a huge win for
Speaker 1: solar towers. So it's a lot of different questions along
Speaker 1: those lines. Obviously, there are other questions to ask why
Speaker 1: is the carbon footprint of actually building the solar tower?
Speaker 1: But I would argue that whatever it is, it probably
Speaker 1: is significantly less than the carbon footprint produced over the
Speaker 1: lifetime of a coal plant or a gas plant or
Speaker 1: oil plant. I think that's a pretty fair assumption, but
Speaker 1: it still could be a very large upfront carbon footprint
Speaker 1: creation there. So that's kind of the approach that I
Speaker 1: wanted to talk about, this idea of being able to
Speaker 1: generate electricity twenty four hours a day using sun power
Speaker 1: without it being a solar panel, and I thought it
Speaker 1: was a really cool approach to that, something that could
Speaker 1: really get around a tricky problem with solar power, because
Speaker 1: I know a lot of critics point out, hey, if
Speaker 1: the sun's not shining, then you're not making electricity. Well,
Speaker 1: that's true with your traditional solar panels, but not with
Speaker 1: solar towers, assuming that you don't enter into cataclysmic event
Speaker 1: where you've got crazy overcast skies for a really long time,
Speaker 1: in which case, if we do have that, we're going
Speaker 1: to have other problems besides where we get our electricity.
Speaker 1: Oh and you might want to know how much electricity
Speaker 1: can one of these facilities generate. It would be good
Speaker 1: for me to tell you that. So Solar Reserve says
Speaker 1: that depending on the plant design, it can generate between
Speaker 1: fifty and two hundred megawatts over electricity, and one megawatt
Speaker 1: is enough power to supply around a thousand homes. So
Speaker 1: you're talking about with one solar tower facility between fifty
Speaker 1: thousand and two hundred thousand homes. Obviously, there are a
Speaker 1: lot of cities that are bigger than that, and in
Speaker 1: order to supply the electricity for those cities, you would
Speaker 1: need multiple solar tower facilities to do that. And again
Speaker 1: that's another question is where would this be most appropriate.
Speaker 1: Obviously a lot of desert towns that have medium to
Speaker 1: small populations, this would be an amazing approach to generating
Speaker 1: electric but it might not work for someplace like New
Speaker 1: York city for multiple reasons, the population size, the lack
Speaker 1: of land to dedicate to solar power. Obviously, that's another issue,
Speaker 1: is that if you are going to dedicate a land
Speaker 1: to a solar tower facility, you're not able to use
Speaker 1: that land for other stuff, at least not easily, So
Speaker 1: that's another consideration. Obviously, you don't want to end up
Speaker 1: going to a place where you're dedicating land that could
Speaker 1: be otherwise used for a more productive purpose, possibly not
Speaker 1: energy related. It might be food related, or water or
Speaker 1: something along those lines. So a lot of things to
Speaker 1: take into consideration, but I think it's a very elegant
Speaker 1: approach to generating electricity in using a renewable resource the
Speaker 1: Sun's energy, and very low impact to the environment. The
Speaker 1: mountain salts are inert, they're not dangerous. They're obviously dangerous
Speaker 1: in their temperature. You would not want to touch them
Speaker 1: while they're at one thousand and fifty degrees fahrenheit, but
Speaker 1: they're not dangerous to the environment. And these, again the
Speaker 1: systems are separate. The water system and the salt system
Speaker 1: are separate from each other. So I think it's a
Speaker 1: really interesting approach. Now I'm curious to hear what you
Speaker 1: guys think about the most promising energy sources for the future.
Speaker 1: Do you really think that solar power is going to
Speaker 1: become a major way to offset our electricity generation. I'm
Speaker 1: pretty sure. I feel fairly confident it's never going to
Speaker 1: be the primary way we generate electricity. I don't think
Speaker 1: it's practical enough to be our primary, but I certainly
Speaker 1: see it as a very strong contender for a support system,
Speaker 1: something that can offset some of our electricity needs. But
Speaker 1: what do you think? Do you think there are other
Speaker 1: ones that are better? Do you think wind power is
Speaker 1: better than solar? Or maybe maybe you think hydropower is better,
Speaker 1: Maybe think geothermal. Maybe you're looking for that nuclear fusion
Speaker 1: approach if that break If there is a breakthrough nuclear fusion,
Speaker 1: that would be an enormous benefit to all of humanity
Speaker 1: because we would suddenly be capable of going into an
Speaker 1: era of energy surplus, which would be phenomenal. And I
Speaker 1: hope it happens. Hope you enjoyed that classic episode of
Speaker 1: tech Stuff how solar towers work. I might need to
Speaker 1: do an update on the various ways that we can
Speaker 1: use solar power to generate electricity. If you have suggestions
Speaker 1: for topics I should cover in future episodes of tech Stuff.
Speaker 1: Let me know by using the iHeartRadio app, which is
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